The present disclosure generally relates to optical cable assemblies and, more particularly, optical cable assemblies having variable current limits.
Benefits of optical fiber include extremely wide bandwidth and low noise operation. Because of these advantages, optical fiber is increasingly being used for a variety of applications, including, but not limited to, broadband voice, video, and data transmission. Active optical cables have electrical connectors that communicate data by optical data signals over one or more optical fibers. Particularly, each connector of the active optical cable includes an active optical circuit that converts the electrical data signals present at the connector into optical data signals for transmission over the one or more optical fibers. The connector at the opposite, distal end of the optical cable receives the optical data signals and another active optical circuit converts the optical data signals back into electric data signals for receipt by a connected electronic device.
It may be desirable for the active optical cable to also provide electric power over its length to a connected electronic device. For example, the active optical cable may be configured as a universal serial bus (USB) cable that provides electrical power provided by one electrical device (e.g., a host device) to another electrical device (e.g., a slave device) over one or more electrical conductors within the cable. However, due to ohmic losses in the one or more electrical conductors, the length of the cable is limited. The greater the length of the cable, the greater the voltage drop from one end of the cable to the other. Additionally, the active optical circuits in both ends of the active optical cable draw power from the input voltage of the host device. The voltage drop due to the ohmic losses in the one or more electrical conductors, as well as the power draw of the active optical circuits, may cause the electrical power at the distal end of the optical cable to be outside of specifications. Thus, the active optical cable may be incapable providing enough power to the distally connected electrical device.
If the current is not limited by the active optical cable, the connected device may attempt to draw more current than is available. This may lead to a brown-out and/or damage to electrical components. Electrical cables may communicate current limit requirements of a host device to a connected device by way of side-hand communication on additional electrical conductors. However, active optical cables may not include such additional electrical conductors because they add additional weight, size and cost. Thus, current active optical cable assemblies are not capable of communicating host current limit requirements from a host connector coupled to the host and a device connector coupled to a device.